Production of dihydroxyfluoboric acid



Patented Oct. 14, 1947 4 UNITED ,STATE S 2,429,147 s PATENT OFFICE PRODUCTION OF DggDROXYFLUOBORIC Wayne E. White, Plum Township, Allegheny County, Pa., assignor to Aluminum Company of America, a corporation of Pennsylvania This invention relates to the production of; di-

hydroxyfluoboric acid, and it is an object of the invention to provide a method of producing dihydroxyfluoboric acid which is efficient and economical.

Dihydroxyfluoboric acid is a viscous liquid having a boiling point of about 160 C. The methods which have been proposed heretofore for its preparation have in all instances been subject to objection on one or both of the grounds of lack of efliciency of the reaction involved and the expensive reagents and equipment required.

In accordance with this invention dihydroxyfluoboric acid is produced by reacting together a fluorine compound, boric oxide, and water. Instead of using boric oxide as such, compounds ca pable of providing boric oxide values available for her. In the preferred form of the invention boron trifluoride is the fluorine compound used, it being introduced in the vapor state into a suspension of boric acid in water. The resulting reaction can be expressed as follows:

In carrying out this reaction, if the various reagents are employed in the stoichiometric amounts indicated by the above equation, substantially pure dihydroxyfluoboric acid is produced, and reaction of the reagents is substantially 100 per cent complete. Boron trifluoride va or is readily soluble in water and when dissolved by the water reacts readily, with the result that there is substantially no loss of boron trifluoride in the process.

It is especially desirable that the reactants be used in stoichiometric amounts in order to have an eflicient and economical process. If boric acid in excess of the stoichiometric amount is used, this excess will largely remain undissolved and unreacted. Boron trifluoride is readily absorbed by dihydroxyfluoboric acid, and although an excess of this reactant may not be objectionable in some cases from the standpoint of utility, since its presence may add to the value of the product as a catalyst, it would add to the material costs. Water causes decomposition of dihydroxyfluoboric acid and consequently it is essential that water not be present in excess.

Instead of using gaseous boron trifluoride as the fluorine compound, fluoboric acid can be employed, in which case the following equation indicates the reaction:

If desired, the fluoboric acid can be produced in situ by reaction of a fluoborate, such as calcium 5 Claims. (ores-139) I fluoborate, barium fluoborate, sodium fluoborate,

or potassium fluoborate, with an acid such as sulfuric acid. The fluoboric acid thus produced then reacts in the manner indicated in the above equation.

In another modification of the invention hydrofluoric acid is produced in situ in a mix containing boric oxide and water, and immediately reacts with the latter materials to produce dihydroxyfluoboric acid. For example, hydrofluoric acid can be produced in the presence of boric oxide and water by reaction of calcium fluoride and sulfuric acid, and the hydrofluoric acid then reacts with the boric oxide and water to form dihydroxyfluoboric acid. This procedure is shown in the following equations:

,reac ion n e process, suc as one am can (2) +B 03+H2O+2HB(0H)2Fa be employed, and references herein to bone oxide include boric oxide values provided in that man- 20 In this modlficatlon it is necessary to heat the mixed reagents at a temperature at which Reaction 1 above takes place, and it is convenient to employ a temperature of at least 160 C. so that the dihydroxyfluoboric acid produced in accordance With Equation 2 will be separated from the calcium sulfate by distillation and subsequent condensation of that acid. In those instances in which the dihydroxyfluoboric acid is vaporized, it is advisable to cool the vapors slowly so as to permit recombination of dissociated constituents of the dihydroxyfluoboric acid vapor.

The invention is illustrated by the following examples:

Ertample I 31 grams of boric acid and 27 grams of water were mixed together in a glass container, and 81 grams of gaseous boron trifluoride were fed into the mix. The mixture was heated at about C. for a few minutes to drive ofi excess boron trifluoride present. 122 grams of pure dihydroxyfluoboric acid were thus obtained, which amount was approximately 9'7 per cent of that theoretically obtainable.

Example II 22 grams of sodium fluoborate, 34.7 grams of barium fluoborate dihydrate, 24.7 rams of boric acid, 21 grams of 96 per cent sulfuric acid, and 4 grams of water were mixed together in a glass vessel. This mix was heated at C. for about 30 minutes, the vapors produced being returned to a glass vessel maintained at 25 C. 60 grams of pure dihydroxyfluoboric acid were recovered in the container.

I claim:

1. The method of producing dihydroxyfluoboric acid which comprises mixing together water, ma terial of the group consisting of boric acid and boric oxide, and a fluorine compound in the absefie of available water values excess of the amount converted to dihydroxyfiuoboric acid.

2. The method of producing dihydroxyfiuoboric acid which comprises reacting together boron tri-- fluoride, boric acid, and water in the absence 0;; available Water values in excess of the amount converted to dihydroxyfluoboric acid. I

3. The method of producing dihydroxyfluoboric acid which comprises reacting together water,

boric oxide, and fluoboric acid in the absence of available Water values in excess of' the amount converted to dihydroxyfluoboric acid.

a m thod of producing .aii yaroiiyriuoboric acidv'vhich comprises mixing'together Water, boric oxide, and a fluorine compound in the absence of available water values in excess of the amount g converted to dihydroxyfiuoboric acid, heating the 1 resultant dihydroxyfluoboric acid at a temperature sufficient to cause it to volatilize, and condensing the resultant vapor.

4. The method of producing dihydroxyfiuoborici acid which comprises reacting together water,

boric oxide, and hydrofluoric acid in the absence of available water values in excessof the amount converted to dihydroxyfiuobofic acid; 7

WAYNE E. WHITE.

REFERENCES CITED The following references are of record in the file .of this patent:

Cellulose Esters, Chemical Abstracts, vol. 34,

page 7108-.- Publishd y amen-c lea- 1 s 

